Electric safety lamp



Jan. 22, 1935; T. ASAKAWA ELECTRIC SAFETY LAMP Filed Nov. 16. 1955 fivI EN TUB. TURAJ-AEAKAI I Jf! BY Q a Patented Jan. 22, 1935 PATENT OFFICE ELECTRIC SAFETY LABIP Toraji Asakawa, Tokyo, Japan, assignor to General Electric Company, a corporation of New York Application November 16, 1933, Serial No. 698,310

' In Japan November 19, 1932 3 Claims.

My invention relates to electric safety lamps for use in locations in which explosive gases are apt to be present, such as mines and factories.

Ordinary electric incandescent lamps cannot be used safely in the presence of explosive gases due to the fact that if the bulb of the lamp should be broken, the said gases coming in contact with the heated filament would cause the said gases to be ignited with a resultant ex- 0 plosion.

According to my invention the lamp comprises a bulb having a filament and an inert gas therein and a transparent or translucent shield or envelope surrounding said filament, said shield having a plurality of small openings therein, preferably at the top and bottom, to permit the circulation of said inert gas through said shield or envelope. If the bulb should be broken, the inert gas inside of the shield prevents an instantaneous influx of explosive gas into said shield, thus preventing said explosive gas from coming into contact with said filament until after it has burned through and cooled down. Even if the explosive gas does enter the shield and becomes ignited therein, the combustion will be confined to the inside of the shield without igniting the outside gas.

Further features and advantages of my invention will appear from the following detailed description thereof and from the drawing.

The drawing is a perspective view, partly broken away, of a lamp comprising my invention.

Referring to the drawing, the lamp comprises a base 10 and bulb 11 having a filament 12 therein and containing an inert gas such as argon or nitrogen. The filament 12 isconnected to lead wires 1314, portions of which are sealed in the press 15 of a stem tube 16. A shield or envelope 1'7, preferably a glass bulb, is disposed in the bulb 11 so as to surround the filament 12. The said envelope 17 is supported independently of the said bulb 11, by support wires 18, 19, 20, 21 (which may be made of nickel) extending from an arbor 22 which extends from the stem 16. The envelope 1'7 shown in the drawing is bell shaped or cylindrical with the lower end closed, said lower end having a plurality of small openings 23 therein. The upper end of envelope 1'! is preferably open and is covered with a metal screen 24 surrounding the stem tube 16. In assembling the lamp the mount, comprising the stem tube, filament, lead wires and support wires, may be readily inserted in the said envelope 1'! through the open end. The lamp may be modified by fusing the open end of envelope 17 to a portion of the stem tube 16 and providing that end of the envelope with a plurality of openings, instead of a screen.

When using the lamp in the presence of an explosive gas, if the bulb 11 should be broken, the explosive gas will surround the outside of the envelope 17 and then slowly enter said envelope through the openings therein by displacing the inert gas in said envelope. However, this procedure takes place comparatively slowly so that the filament 12 burns through and cools down before said explosive gas comes in contact with it. Even if the gas did ignite in the envelope 17, the combustion would be confined therein without igniting the gas on the outside.

A metal protective shield or sleeve 25 may be provided on the lamp surrounding a portion of the bulb 11 to protect the inner envelope 17 from breakage. Said shield 25 is provided with a multiplicity of openings 26 to allow light to pass therethrough.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. An electric incandescent safety lamp comprising a bulb, an inert gas filling and a filament in said bulb, a light transmitting envelope surrounding sail filament, said envelope being open at one end, a metal screen covering said opening, and a plurality of small openings in the opposite end of said envelope.

2. An electric incandescent safety lamp comprising a bulb, an inert gas filling in said bulb, a mount in said bulb comprising a stem, a filament, leading-in wires, and support wires, and a light transmitting envelope surrounding said mount and supported by said support wires, said envelope having a multiplicity of small openings therein.

3. An electric incandescent safety lamp comprising a bulb, an inert gas filling in said bulb, a mount in said bulb comprising a stem, a filament, leading-in wires and support wires, a light transmitting envelope surrounding said mount and supported by said support wires, said envelope being open at one end, a metal screen covering said opening and surrounding said stem, and a plurality of small openings in the opposite end of said envelope.

TORAJI ASAKAWA. 

